Articulated ankle joint with inner and outer races for universal movement

Abstract

An artifical ankle joint for use as an ankle between a foot prosthesis and leg prosthesis in an artificial limb. The artificial ankle joint includes a foot plate attached to a foot prosthesis, a leg plate attached to a leg prosthesis, a stem assembly and bearing assembly connected between the plates in which the bearing is a spherical bearing oriented vertically and including an inner race connected to the leg plate about an axis generally horizontal when the ankle joint is in use and an outer race connected with the stem assembly. Resilient structure extends between the plates for providing a degree of resistance to relative movement of the plates and includes a heel spring enclosing the stem assembly and a toe spring spaced from the heel spring with both the toe and heel springs extending between the plates. The stem includes a unitary or two piece unit anchored to the foot plate at one end and including a vertically disposed spherical bearing assembly connected to the leg plate at its other end to enable relative pivotal movement of the foot prosthesis in any angular direction with respect to the leg prosthesis and enabling limited swivelling movement of the foot prosthesis in relation to the leg prosthesis. This enables the articulated ankle to closely simulate all movement capabilities of a natural ankle.

What is claimed as new is as follows: 
     
       1. An articulated ankle joint comprising a foot plate for attachment to a foot prosthesis, a leg plate for attachment to a leg prosthesis, a stem assembly interconnecting said plates, said stem assembly being positioned at a heel portion of the foot prosthesis, said stem assembly including a spherical bearing for providing relative movement between the plates, a heel coil spring encircling the stem assembly and engaging said plates for reacting between the plates and providing a degree of resistance to said relative movement between the plates, and a toe coil spring connected between the plates forwardly of the stem assembly for providing resistance to said relative movement between the plates, said spherical bearing being vertically disposed and including an inner race connected with said leg plate and an outer race connected with said stem assembly, said stem assembly including a vertically disposed annular ring receiving said outer race, said inner and outer races of the spherical bearing including partial spherical surfaces to enable universal movement between the inner race and outer race, said leg plate including a bearing housing having a cavity therein receiving said ring and spherical bearing, a retaining pin extending transversely of said cavity and through said inner race and into said bearing housing thereby connecting said inner race to the leg plate for relative movement between the bearing housing and stem assembly. 
     
     
       2. The joint as defined in claim 1 wherein said stem assembly is connected with said foot plate with the annular ring being rigid with the upper end of the stem assembly, said heel spring engaging the foot plate in peripheral encircling relation to the stem assembly and engaging the leg plate in encircling relation to the bearing housing and ring to resiliently resist relative movement between the plates. 
     
     
       3. The joint as defined in claim 1 wherein said stem assembly includes a cylindrical projection integral with the foot plate and extending upwardly therefrom, a post engaging the upper end of the projection and including a depending sleeve telescopically engaging the projection, said annular ring being integral with the post and fastening means extending through the projection and securing the sleeve to the projection to enable assembly of the components and loading of the springs during assembly. 
     
     
       4. The ankle joint as defined in claim 3 wherein the upper end of said projection and said post include interengaging socket and projection means to preclude relative rotational movement between said projection and said post in spaced relation to said fastening means. 
     
     
       5. The ankle joint as defined in claim 1 wherein said stem assembly includes an upstanding tubular projection rigid with said foot plate, a post engaging the upper end of the projection, a sleeve depending from said post and telescoped into said projection, said sleeve being internally threaded, and a screw threaded fastener extending through the foot plate and threaded into said sleeve for rigidly mounting the post on said projection. 
     
     
       6. An articulated ankle joint comprising a foot plate for attachment to a foot prosthesis, a leg plate for attachment to a leg prosthesis, a stem assembly interconnecting said plates, said stem assembly including a generally vertically oriented spherical bearing for allowing relative movement of the plates, said spherical bearing including an inner race, horizontally disposed pin means connecting said leg plate to said inner race, an outer race rigid with said stem assembly, and resilient means between the plates for providing a degree of resistance to relative movement of the plates with respect to each other, said stem assembly including post means rigid with and upstanding from said foot plate, said spherical bearing being mounted at the upper end of said post means and oriented in a vertical plane, said horizontal pin means being disposed transversely of said foot prosthesis and said leg prosthesis and enabling relative pivotal and rotational movement of said plates, said leg plate including a vertically disposed cavity receiving said spherical bearing and an upper end of said post, said pin means extending transversely of said cavity and through said inner race, said resilient means including a pair of spaced coil springs connected to said plates, one of said springs being at the heel portion of the plates and the other spring being at the toe portion of the plates. 
     
     
       7. The ankle joint as defined in claim 6 wherein said post is of one-piece construction and includes a base, fastener means rigidly securing said base to said foot plate. 
     
     
       8. The ankle joint as defined in claim 6 wherein said post is of two-piece construction and including a lower part of unitary construction with the foot plate and fastener means securing an upper part of the post to the lower part. 
     
     
       9. The ankle joint as defined in claim 8 wherein said upper and lower parts of said post are telescopic and include means preventing relative rotation. 
     
     
       10. The ankle joint as defined in claim 6 wherein said coil spring at the heel portion of the plates being disposed in enclosing relation to said post means and having an upper end engaged with said leg plate in peripheral relation to said cavity to resist relative movement of said plates in all directions permitted by said spherical bearing and pin means. 
     
     
       11. The ankle joint as defined in claim 10 wherein said post means includes a tubular projection extending upwardly from said foot plate and including a hollow interior and a post member having a downwardly facing horizontal flange engaged with an upper end of said projection and a screw threaded fastener extending into threaded engagement with the post member through said projection to enable assembly of the ankle joint and loading of said springs. 
     
     
       12. The ankle joint as defined in claim 10 wherein said post means includes a one piece post having a base attached to said foot plate and the spherical bearing at an upper end thereof received in said cavity, said spring at the heel portion of the plates encircling the one piece post and having an upper end engaged with said leg plate at a lower end of said cavity to resist relative movement between said plates in all directions. 
     
     
       13. The ankle joint as defined in claim 12 wherein said post member includes a tubular sleeve telescoped into said projection with the sleeve being internally threaded for threaded engagement by said threaded fastener, an upper end of said projection and said flange on said post member including interengaging radial recess means and projection means to prevent rotation of the post member in relation to the projection when the post member and projection are assembled by threading the fastener into said sleeve.